Initial Graphics Exchange Specification (IGES ) is a neutral file format designed to transfer 2D and 3D drawing data between dissimilar CAD systems. The IGES standard defines two file formats: fixed-length ASCII, which stores information in 80-character records, and compressed ASCII. The IGESIMPORT and IGESEXPORT commands support only the fixed-length format.
Under ideal conditions, translation preserves the appearance and functionality of entities. However, this process has limitations, and some data will not be preserved in a round trip to IGES and back.
For example, when exporting to IGES, a 2D polyline is translated as IGES entity 106:12. When importing from IGES, entity 106:12 translates to a spline. Hence, if you use IGESIMPORT to read a file created by IGESEXPORT, the resulting drawing may not be identical to the original drawing.
Similar data loss may occur when transferring data between AutoCAD and another CAD system, using IGES. Usually, a one-time translation to or from IGES does not pose a serious problem. However, data loss can become a concern if drawings are repeatedly translated in and out of IGES.
Inspect the conversion tables of the IGES translators of both the source CAD program and AutoCAD. Get to know what entities are supported. Restructure the drawing to minimize the usage of objects that require compromises and substitutions.
See the conversion table for IGESIMPORT for specific details of the scope of the IGES translator.